Well-known monitoring devices are utilized preferably in department store showrooms and serve to prevent an unnoticed removal of goods in the case of showroom models, in particular removal of upscale electronic devices, which are generally freely accessible to customers for testing purposes.
Purely mechanical theft protection systems provide fastening of the product with a thin steal wire or a plastic line, which is firmly connected with a fastening piece that is glued to the product. In addition, the steal wire or plastic line is attached to an object that cannot be transported, such as, for example, the display shelf or a larger device.
Apart from this, electronic monitoring devices are well known. Their main advantage lies in the possibility of detecting sabotage or earlier removal attempts and thus activating an early corresponding alarm.
With traditional electronic monitoring devices, this is achieved by mounting a sensor element to the product. In particular, the element is connected with a central processing unit by way of a cable. The sensor element delivers a measured variable that already changes with the attempt to detach the sensor element or the cable from the product. The processing unit processes the measured variable supplied by the sensor element and if necessary activates the alarm.
Popular sensor elements may include microcircuits or optical transmission systems or wire strains gages. Based on their size, however, sensor elements with microcircuits are in most cases unsuitable for protecting modern cell phones or electronic schedule books. Furthermore, correct mounting of the sensor element to the product housing is very difficult due to the complex housing shape—in particular, for very modern devices comprising many curvatures.
With wire strain gages and optical detector equipment, very small sensor elements are possible in principle; however, these feature an equally high price and are reusable only to a limited degree after forceful removal from the product.
Another version of electronic monitoring systems is known from EP 0 663 656 B1. The patent document discusses an electronic conductor loop on a sensor element equipped with predetermined breaking points. The conductor loop is destroyed through removal of the sensor element from the product during a theft attempt so that the sensor element is not reusable.